AIMS: SECRETO involves five principal fields of investigation: (1) Stroke triggers and clinical risk factors; (2) Long-term prognosis (new vascular events, functional and psychosocial outcomes); (3) Abnormalities of thrombosis and hemostasis; (4) Biomarkers of e.g. inflammation, atherogenesis, endothelial function, thrombosis, platelet activation, and hemodynamic stress to characterize postulated cryptogenic stroke mechanisms; and (5) genetic study, including genome-wide association and candidate gene studies as well as next-generation sequencing approach. All analyses consider cardiac functional and interatrial structural properties as a possible mediator. Furthermore, SECRETO Family Study (substudy) aims at collecting extensive family history of thrombotic events from informative patients being screened for SECRETO main study and collect genetic samples from all consenting family members for whole-genome sequencing.